Radio system for measuring distance by phase comparison



Nov. 14, 1950 T. M. MANLEY RADIO SYSTEM FOR MEASURING DISTANCE BY PHASE COMPARISON Filed March 1, 1946 DISTANCE 3 Sheets-Sheet 1 INDICATOR T 32 I'M LOCAL STATION I 30 3| d Q i710 AUDIO PHASE OSCILLATOR SHIFTER TRANSM'TTER 11 1 RED%ECATTON J 4 KEYER 34 Box CIRCUIT 33 k 1: 6 v A 16 Y? MOTOR PHASE CONTROL COMPARISON RECEIVER CIRCUIT CIRCUIT H5 H4 l2 FIG. I

REMOTE STATION 33 3| 37 7 RECEIVER PHASE MODULATOR TRANSMIT A SHIFTER PHASE MONITOR L25 INVENTOR.

THEODORE M. MANLEY Nov. 14, 1950 T. M. MANLEY 2,529,510

RADIO SYSTEM FOR MEASURING DISTANCE BY PHASE COMPARISON Filed March 1, 1946 s Sheets-Sheet 2 DISTANCE INDICATOR izlo TRANSMITTER v 3 9 3| I AUD|0 PHASE OSCILLATOR SHIFTER GEAR I REDUCTION 2 BOX I I I S U R Q A E 42 I WAVE I GENERATOR [U 4 I I I I I40 I PHASE I I I I OOMPARISONI I MOTOR I CIRCUIT I I CONTROL I u l I LE'TE' I 50 H {12 W I PULSE V \I I RECEIVER I FORMER I I i L l I \63 q l l 33' m KEYER CIRCUIT INVENTOR. THEODORE M.MANI EY FIG.3

,4 fi o/77g T. ML MAN LEY Nov. 14, 1950 RADIO SYSTEM FOR MEASURING DISTANCE BY PHASE COMPARISON Filed March 1 1946 5 Sheets-Sheet 3 R505! VEI? 7'0 TRANSMITTER AND PHASE sou/ 4 RISO/V CIRCUIT IN l/E/V TOR THEODORE M. MANLEY A TTOR/VEY Patented Nov. 14, 1950 RADIO SYSTEM FOR MEASURING-DISTANCE BY PHASE COMPARISON Theodore M. Manley, Ann Arbor, Mich.

Application March 1, 1946, Serial No. 651,408

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 4 Claims.

aeroplane of his varying proximit to a transceiver at a remote station located at a ground station, within another aeroplane, or elsewhere by the use of radio equipment and energy.

Another object of the invention is to provide radio means for warning an aeroplane pilot of his proximity to a dangerous object.

Another object is to provide a distance indicating radio system whereby a substantially continuous indication of distance can be obtained between a pluralit of different local stations and a single remote station with a minimum of interference and interaction.

With the above and other objects in view that will be apparent to those who are informed in the field of radio transmission, illustrative embodiments of the present invention are shown in the accompanying drawings; wherein:

Fig. l is a block diagram of a radio circuit at a local station;

Fig. 2 is a block diagram of a radio circuit at a station that is remote from the local station;

Fig. 3 is a block and schematic diagram of the circuit that is shown in Fig. 1, but in greater detail; and

Fig. 4 is a schematic diagram of the keyer circuit part of the circuit that is shown in Fig. 1.

In the embodiment of the present invention that is presented herein, distance is measured by the time required to transmit a radio signal from a local station to a remote station and an answering signal to return. The time is indicated as the phase delay between a periodic modulation transmitted on a first carrier and the same modulation received back on a second carrier; the transfer of the modulation from the first carrier to the second carrier is made at the remote station effectively without loss of phase, since the dela introduced at the transfer is adjusted to be an integral multiple of a cycle. The phase delay is read directly upon an indicator calibrated in miles.

In the present invention it is simpler to limit the extreme range over which distances are to be measured to ranges whose corresponding phase delays are not greater than 360 degress. Thus since the velocity of radio propagation is 186,000 miles per second, the time of travel of a radio signal over 200 miles is ,6 second, and since the present invention involves travel out and back, a

range of 100 miles would correspond to 360 degrees phase delay in a 930 cycle audio signal. For shorter ranges a higher audio frequency would be used. The circuit that is shown in Fig. 1 is illustrative of a circuit at a local station which is provided with a distance indicating instrument. The circuit shown in Fig. 2 is illustrative of a circuit at a remote station to which distance from the local station shown in Fig. l is to be measured.

The radio circuit at the local station comprises a signal generating means, such as an oscillator l which generates an audio frequency sine wave voltage 30. Part of the output from the oscillator I is impressed upon a suitable phase shifter 2 and another part is impressed upon a phase comparison circuit I4 through a conductor i3. The output of the phase shifter 2 is shifted in phase from that of the oscillator l depending upon and proportional to the angular position of a. shaft represented by a dash-line 4 in Fig. 1. This shaft is a part of a motor rotor shown in Fig, 3. The shaft 4 mechanically couples the phase shifter 2 with a motor, part of a motor control circuit I5, through agear reduction box 6. The shaft 4 is also coupled mechanically with an indicating arm 1 of continuously reading distance indicator 8 provided with a calibrated scale over which arm 1 passes in the usual manner. The phase shifter 2 may be of the Helmholtz type, or may be an equivalent circuit comprising variable capacitors and resistors, not shown, under the control and operation of the shaft 4'.

The output voltage of the phase shifter 2 is applied to a transmitter 9 by a conductor 3 and serves to modulate, as indicated by the envelope 3|, a first radio signal 32 that is-generated in the transmitter 9 and radiated from an antenna Ill.

The frequency of the first radio signal 32 from transmitter 9 may have any suitable value'and preferably a value within the very high frequency range to minimize the effect of interference between stations and also of transients. The frequency of the first radio signal 32 from transmitter 9 may be either a single frequency or a desired number of different frequencies, and may be tuned by suitable means upon the operation 3 of push buttons, switches, or the like, in a usual desired manner.

A receiving antenna ll part of the local station, intercepts radio signals from a remote station shown in Fig. 2 and applies them to a receiver l2. These signals are illustrated by the wave 34. The received signals are demodulated in receiver l2 and the audio modulation output of the receiver I2 is applied in the phase comparison circuit M. A keyer circuit l6, that preferably is an electronic switch to be described hereinafter, permits the energization of the circuit of the transmitter 9 and of the phase comparison circuit l4.

A part of the output from the oscillator is applied to the phase comparison circuit M, as stated previously. The phase comparison circuit i4 operates to compare the phase of the audio output of receiver l2 with that of the audio sine wave output 30 of oscillator parison circuit l4 also controls the direction of rotation of the motor rotor 60 (Fig. 3) which is a part of the motor control circuit IS.

A block diagram of a preferred circuit at the remote station is shown in Fig. 2 of the accompanying drawings. In the circuit there shown a receiving antenna 20 intercepts signals 32 radiated from the sending antenna l0. These intercepted signals are applied to a receiver 2| where they are detected or demodulated and applied through a lead 22 to a phase shifter 23 and to a phase monitor 25. The phase shifter 23, that may be substantially a duplication of the phase shifter 2 in Fig. 1, applies its output to a modulator 24. applied to a transmitter 26 and also to the phase monitor 25. The transmitter 26 generates a second radio signal, which is represented by modulated carrier 34. This second radio signal 34 is modulated by the audio signal from modulator 24 to provide the envelope 33 thereon. The second radio signal 34 is radiated or transmitted from an antenna 21 for interception by the receiving antenna II at the local station shown in Fig; 1.

Signal from the radiating antenna 21 may be of any desired frequency to which the receiver 12 can be tuned. The receiver I2 is tuned to the answering radio frequency signal radiated from the antenna 21.

In a similar manner the receiver 2| is tunable to any frequency from the transmitter 9 that can be radiated by the antenna Ill. The carrier frequencies that are chosen for the first signal 32 that is radiated by the antenna l0 and the second signal 34 radiated by the antenna 21 should be such as to produce a minimum or negligible interaction, so that the receiver |2 does not pick up signal 32 from the antenna l0 and so that the receiver 2| does not pick up signal 34 radiated.

by the antenna 21. The selectivity of the receivers I2 and 2| also affect the choice of frequencies as outlined above. The transmitters 9 and 26 and the receivers I2 and 2| are usual forms of equipment.

Operatively, the audio oscillator provides an audio frequency wave 30 that is advanced in phase as it passes through the phase shifter 2 and is then applied as modulation to the carrier that is provided by the transmitter 9. The resultant first modulated signal 32 is radiated by the antenna l0 and is intercepted at the remote station by the antenna 20. The receiver 2| demodulates this first signal wave 32 received from the antenna 20. The resulting audio signal is applied as modulation upon another radio fre- The phase com- The output from the modulator 24 is quency carrier provided by the transmitter 26. The modulated carrier supplies the second radio signal 34 which is radiated by the antenna 21.

At the local station this second radio signal is intercepted by the antenna II and passed to the receiver l2. In receiver l2 the signal is demodulated and this audio output is passed to phase comparison circuit l4. The phase comparison circuit l4 serves to compare the phase of the audio signal 30 that is generated by the oscillator with the phase of the audio voltage which has passed through the cycle of transmission reception, retransmission and rereception. It is seen that the two audio signals compared are of the same frequency. The phase comparison circuit l4, as previously stated, operates to control the rotation of the motor rotor 60 in the motor control circuit IS. The motor rotor 60 rotates in one direction or in the opposite direction depending upon whether the phase of the output of receiver l2 leads o lags the phase of the reference signal 30 from the oscillator If the phase of the output of receiver l2 lags the phase of the reference audio sine wave voltage 30, the motor rotor 60 causes the phase shifter 2 to advance the phase of its output and so to decrease the amount of phase difference between the two signals in phase comparison circuit l4 to zero. If the phase of the output of receiver l2 leads the phase of the reference audio voltage 30, the motor rotor 60 is caused to rotate in the opposite direction until the phases in phase comparison circuit l4 are balanced. In either case the total amount of angular rotation measured from a fixed origin of the shaft 4 that is necessary to maintain a balance between the phases of the output of receiver I2 and the output of audio oscillator is a measure of the phase shift that results from the transmission of the audio modulation to the remote station and return. (It is to be understood that transmitters 9 and 26 and receivers l2 and 2| introduce no phase shift of modulation.) The disposition of the arm 1 on the scale of the distance indicator 8 indicates directly and continuously the distance between the local station and the remote station. By operating the system in short pulsations of one-twentieth second or less every two seconds, the system is open for considerable time between successive pulsations for other desired communications.

During the brief interval of the time during which the signals are being transmitted and the two phases are being compared, impulses are supplied to the motor circuit I5 which in turn varies the phase shifter 2 through an appreciable portion of the 360 total available phase change. The transmissions are repeated at predetermined time intervals, as for example at two second intervals. The distance indicated by the arm 1 upon the scale of the indicator 8 is correlated with the phase delay introduced by phase shifter 2. The distance indicated will be caused to vary in small steps in accordance with the change in distance between the local station and the rev mote station during the time intervals.

The effect is to provide the local station with a substantially continuous indication of the distance between the local station and the remote station. The involved radio channels are in use inc the distance from it to the same remote station, for signal exchange, or the like. It will thus be seen that distance measurements made at approximately a predetermined rate and for predetermined time durations are provided for.

'Ihekeyer circuit l6 controls the operation of the system so that signals are sent and received during only a small fraction of a cycle of operation. The keyer circuit. l6 supplies a blocking signal to transmitter 9 and to phase comparison circuit 14 during-the greater portion of a cycle of two seconds. ..Once.in the cycle, the blocking signalis removed for one-twentieth of a second and during that interval the equipment is'functioning. This provision materially. reduces the interference between this equipmentand other transmissions, and in particular, interference between a multiplicityof these devices all onthe same pair of frequencies.v Further means, to be described later, are providedin the keyer circuit N to prevent operation of the device if a second device is in operation at the instant that the keyer circuit It would normally unblock the 45 respectively. Direct current return path to" ground for the screen grids of the tubes 44 and 45 is provided by resistors 48 and 49.

. The pulse former 4| .part of the phase comparison circuit I4 is used to form a train of pulses 50 of negative voltage from the sine wave which is the output of receiver l2. The train of pulses 50 has the same frequency as the sine wave from which it is formed and a constant phase relative thereto. The negative voltage.

pulses 59 are applied simultaneously to the cathodes of the thyratron tubes 44 and 45. A positive bias voltage from the keyer circuit I5 is applied intermittently to the control grids of the thyratron tubes 44 and45 through the resistors 5| and 52, respectively, for the purpose lof permitting the energization of the tubes 44 and 45 for a predetermined period of time as for onetwentieth second every two seconds. The plates of tubes 44 and 45 are connected push-pull to the divided secondary (comprising windings'54 and 55) of an alternating current transformer 53 to which 400 cycle alternating current is supplied through primary 6|.

During the one twentieth second during which the device is operating the control grids of tubes 44 and 45 are rendered sufiiciently positive by voltage from keyer circuit is to permit the tubes 44 and 45 to function, other conditions being plate current swinging to the negative part of its cycle. It will be noted that since square waves 42 and 43 are of opposite phase both are not positive simultaneously. Therefore a negative voltage pulse of train will fire at any one time only one of the tubes 44 and 45. Accordingly, as train 50 leads or lags the phase of the voltage 39 from audio oscillator l a negative voltage .pulse of train 50 will fire one or the other of the tubes 44 and 45. In the circumstance that pulses of train 50 occur at the instant that both square waves 42 and 43 are changing from positive to negative and vice versa, neither of the tubes 44 or 45 will fire. This corresponds. as will appear, to phase shifter 2 being in precise adjustment for phase balance of transmitted and received signal and arm I on indicator 8' indicating precise range.

I The plate circuits of tubes 44 and 45 are completed by connecting the junction of windings 54 and 55 with one field coil 59 of a two-phase induction motor having'rotor 60 as shown in Fig. 3. The other field coil 51 receives its current from a secondary winding 55 of transformer 53. The current in coil 51 is shifted 90 degrees in phase to the current in coil 59 by the action of series capacitor 58. Current passes through coil 51 continuously but current passes through coil 59 only when tube 44 or tube 45 is fired. Accordingly, the motor turns only when tube 44 or tube 45 is fired, and the direction of rotation is one way or the opposite way according to which tube 44 or 45 is fired. If both tubes 44 and 45 were to fire simultaneously, no current would flow through the coil 59 and the motor rotor 60 would not turn. The resultant rotation of the motor rotor 60 turning the shaft 4 connected. to the phase shifter 2 determines the disposition of the distance indicating needle I on thescale of the indicator 8, and thereby registers the distance between the local station and a remote station.

There is shown in Fig. 4 a detailed circuit for the keyer circuit 16. Gas tube 12 is shown connected as a conventional generator of sawtooth voltage 90 having a resistor 14 in the plate lead and a capacitor 13 between plate and cathode which determine a period of about two seconds. Grid bias is supplied by battery 69 in series with a load resistor 10. v

The sawtooth voltage 90 is difierentiated by 'a condenser 15 and a-resistorli to provide a resultant pulse 92-." The resultant pulse 92 is apfavorable. During the rest of a two second interval the voltage from keyer circuit I5 is so negative that the tubes 44 and 45 will not fire under any circumstances. I

A negative pulse of train 50 is not of sufiicient voltage to fire the thyratron tubes 44 and 45 of itself. However, in the presence of positive voltage on the plate from thealternating current supply and of positive voltage .on .the screen from square waves 42 or'43 either of thyratron tubes 44 or 45 will fire and continue to draw plied to the grid of an electronic tube 16 .part of a usual type of one-shot" multivibrator circuit; Plate current to the pair of multivibrator tubes 15 and I1 is supplied through resistors 18 and 19, respectively. The resistor 'is'interposed between the grid of tube- I5 and the B+ power supply. Multivibrator output from the plate of the .tube 16 is applied through a capacitor to the grid of an electronic tube 8!. The grid of the tube 8| is grounded through a resistor 82 and; a tappedpart of another resistor 83. The ungrounded end of the resistor 83 is connected to the negative terminal of a direct current power source 84 that has its positive terminal grounded and, through a resistor to the cathode of the tube 9|. The cathode of the tube 8| is also connected by lead,63 to the junction of the resistors 5| and 52 in the phase comparison circuit l4 and to the transmitter 9.

With the normal bias supplied to the grid of thetube 12 by battery 58, the capacitor 13 charges through the series resistor 14 at an exponential rate until the voltage across the thyratron tube 13 7 is sufficient to cause conduction. The conduction of the thyratron tube I2 discharges the capacitor 18 to a voltage below the ionization potential of the thyratron tube I2 and the discharge stops. Every two seconds this procedure is repeated.

The sawtooth output voltage 80 of tube 12 which is difierentiated by the resistance-capacitance circuit 86, I8 is applied to the grid of the multivibrator tube 18 as previously described. The output of the one-shot multivibrator circuit is taken off the plate of the multivibrator tube 18 and is the square wave 8| of approximately onetwentieth second duration and occuring with each conduction of the thyratron tube 12.

These pulses of square wave voltage 9| are positive-going pulses and are applied to the grid of the electronic tube 8|. The tube 8| is normally non-conducting since its grid is returned to the contact on resistor 88 which is more negative than the cathode of the tube 8|. The tube 8| is not conducting during the two second intervals between signals and hence the voltage at the cathode of the tube 8| is approximately the voltage across the resistor 83 or the voltage supplied by the cathode bias supplying battery 84.

The negative voltage supplied by the battery 84, when applied as bias to various circuits in the transmitter 8 and in the phase comparison circuit l4, render them inoperative. However, when the grid of the tube 8| is driven positive by the intercepted signal pulse, the tube 8| conducts and produces a voltage drop across the resistor 85 which reduces part of the voltage at the cathode of the tube 8|. The circuit components are selected or adjusted so that the value to which the voltage rises is the normal operating bias of the circuits that are controlled and so that normal circuits and components may be substituted for the circuit associations and components that are shown herein within the concept of the present invention.

What I claim is:

1. A system for measuring distance between first and second points comprising, at said first point, means for generating a wave of fixed frequency and phase, a variable phase shifter coupled to said means, a radio transmitter modulated by the output of said phase shifter; means at said second point for receiving the signal from said transmitter and for retransmitting toward said first point a second signal modulated by the same wave as the received signal, a receiver at the first point for receiving said second signal and operation is achieved throughout the duration of the pulse.

Thus the keyer circuit It serves to energize the transmitter 8 and phase comparison circuit H for brief intervals at a periodic rate.

The circuit connected to diode rectifier tube 88 will now be described. The output transformer 88 of receiver I2 is shown connected across a series resonant circuit composed of capacitor 68 and inductance 81. This circuit is tuned to the audio frequency of oscillator I (which is the same for all sets using this system near a single remote station). Any audio signal of this frequency appearing in the output of receiver 2 puts a direct voltage across load resistor 10 and increases the negative bias on the grid of tube 12. By this means the requisite firing potential of the thyratron tube 12 is increased to a value that is greater than the plate supply voltage; the capacitor 18 will continue to charge and the conduction of discharge of the capacitor 13 will be delayed until the interfering signal disappears and tube bias is restored to normal, at which time the thyratron tube 72 will immediately fire. Thus the keyer circuit i8 will not operate to unblock transmitter 8, if there is already being received an interfering signal. It is to be noted that reception of an answering signal to a transmission from transmitter 8 will not block the transmitter because the answer always occurs just after thyratron 12 has already fired and the grid no longer controls.

It is within the purview of this invention to for deriving the modulation component thereof, phase comparing means for providing a voltage having a sign and value in accordance with the relative phase difference of said modulation component and said wave of fixed frequency and phase, a motor for operating said phase shifter in response to the voltage from said phase comparing means, said phase shifter being calibrated in terms of distance, electronic switch means for supplying blocking voltages for the control of the operation of said transmitter and said comparing means connected to be controlled from the receiver at said first point including means for controlling the operation of said switch means in response to the occurrence of signals in said receiver having the frequency of said fixed frequency wave.

first point for generating a sine wave of fixed frequency and phase, a, variable phase shifter coupled to said means for acting upon said first sine wave, and a radio transmitter modulated by the output of said phase shifter; means at said second point for receiving the signal from said transmitter and for retransmitting toward said first point a second signal modulated by the sine wave as the received signal, a receiver at the first point for receiving said second signal and for deriving the sine wave modulation component thereof, phase comparing means for detectin the relative phase difference of said modulation component and said sine wave, said phase comparing means including a square wave generator acting upon the first sine wave from said sine wave generating means to form a square wave having the same frequency as the first sine wave voltage and a fixed phase relative thereto, a pair of gaseous discharge tubes each having at least plate, grid and cathode and having their platecathode circuits energized in opposite polarity by a common alternating voltage. means applying the square wave across the grid-cathode circuit of one of said gaseous discharge tubes in one polarity and across the grid cathode circuit of the other tube in opposite polarity, a pulse former for acting upon a second sine wave voltage from said receiver at the first point of the same frequency as the first sine wave voltage to form a train of sharp pulses having a repetition rate equal to the frequency of the second sine wave voltage and a fixed phase relative thereto. means for applying said second sine wav to said pulse former, means for applying the train of pulses in common to the grid-cathode circuits of said gaseous discharge tubes to drive the grids of said tubes positive with respect to the cathodes, means for deriving from the plate-cathode circuits of said gaseous discharge tubes 9, signal in- -nal and having means component thereoi;

. Q dicativeoithathalicycleoithefirstsinewave voltage in which the pulses of the pulse train tall. and means responsive to the indicative sigassociated therewith for acting upon said phase shiiter to adjust the first sine wave voltage until the phase diii'ere'nce is are. said phase 'shiiter of distance. 7

3. In a system for measuring distance between first and second points, comprising at said first point. means fol-generating a sine wave of fixed frequency and phase, a variable phase shifter coupled to said means. and a radio transmitter modulated by the output or said phase shifter; means.v at said second point. for receiving the from said transmitter and for retransmitting toward said first point a second signal modulated by the M1. a receiver at second signal and for deriving the modulation phase comparing means for detecting 'the relative phase diil'erence 01' said modulation component and said sine wave, means controlled b said phase comparing means for varying said phase shifter until said phase said unblocking' being calibrated in terms same wave as the received sig- 5 A the first point tor receiving said said unblockingpuiaesinresponsetoanyslsnal in said receiver at the first point having the frequency of said first named sine wave. except such signals which occur during the period at an unblocking pulse.

4. The system, according to claim 3, wherein .said means for generating unblocking pulses comprises a sawtooth voltage generator, a ditrerentiator and multi-vibrator circuit, and said delaying means includes means ior filtering i'r'om the output oi said receiver any signal received having the irequency of said first named sine wave. means to rectify said filtered output, and means for applying said rectified and filtered output as additional bias to said i M voltage generator.

THEQDQRE M.

REFEBENCEQ GEE lhe following references are of record in the file of this patent:

UNITED STATES PA Qertifieete oi Con Patent No. 2,529,510

It is hereby certified t above numbered paten t requiring cor Novher is, less at error appears in the lJprintecl specification oi the rectlon as f0 ows:

Column 9, line 27, after the word .for insert said;

and that the said Letters samcsmay conform to th and sealed this Patent should be read as corrected a record of the case in the 9th day of January,

above, so that the Patent Ofi A. D. 1951. 

